The physicochemical surface characteristics of Lactobacillus casei

The surface and interfacial properties of five strains of Lactobacillus cas ei, commonly found in cheese, were investigated in an attempt to identify s urface properties that might be exploited to effect adsorption of the cells onto milk fat globules. All measures of surface hydrophobicity revealed th ese strains to be moderately hydrophobic compared to a reference strain of Mycobacterium smegmatis which was very hydrophobic, in chromatography exper iments, L. casei had no affinity for either hydrophobic (octyl-sepharose) o r control (sepharose) columns in conditions of physiological pH and low ion ic strength, despite a favorable free energy of interfacial interaction (De lta G(IW2)(IF)) as derived from contact angle measurements. Adhesion of L. casei strains to these materials was effected by manipulation of eluent pH and ionic strength. In contrast, adhesion of L. casei strains to n-hexadeca ne concurred with Delta G(IW2)(IF). Surfaces of L. casei strains subjected to X-ray photoelectron spectroscopy exhibited similar amounts of carbon and oxygen but displayed considerable diversity in surface nitrogen and phosph orous contents. Carbon existed predominantly as C-(O, N) and oxygen as -OH on L. casei surfaces but carbon on M. smegmatis surfaces was present predom inantly as C- (C,H) (C) 2000 Academic Press.